The Fundamentals of Us
by summerfell
Summary: A dive into the origins of Kurama and Hiei's relationship, so complex it can only stem from different cycles of trust and betrayal. Explores the three treasures arc in line with The Art of Losing a Fox. This fic is special to me for some reason. Yaoi. KxH
1. Chapter 1

Three things first.

**One**, there are many theories as to exactly why Hiei was acting like a **homicidal maniac** during the first part of the series. This is my take.

**Second**, this, in a way, is also answer to **25thchromosome**'s request of a story delving more into the betrayal of Kurama during the three treasures arc. But that was just one of the betrayals that will happen in this story. There will be a total of five.

**Lastly**, this is also an exposition of number 3 in **The Art of Losing A Fox**. Though this can stand on its own, I recommend reading that ficcie first. It's just a one shot and you can finish it in a couple of minutes, so be patient and do it. Click on my profile and look for it under my stories.

**Disclaimer: **When I get rich, I'll buy the rights to YYH. But right now, I just own and nurse a 10-year old heartache.

**Warnings: **Homosexual content aka YAOI, shonen-ai, BL, however you want to call it. Stop now if you don't like it.

**The Fundamentals of Us**

It was a sunny and otherwise normal afternoon when I realized that even without telling him, Hiei knew something was wrong. He understood me in that way, like a bird a flower. It was not because of the jagan, nor of the lingering stress of the silences before I answered his questions; we've learned to trust each other deeper than the absence of words and the fullness of stares, after all. In fact, the combination of my absence at hours that I should be in my room, and the wilting of the blood roses I always kept at my bedside, were barely clues. Those could be easily explained by distraction.

What gave away my state of desperation was more simple, and its simplicity, more incriminating.

Closing the door with a soil-cracked shoe behind me, I settled my school-fed thinning body on the foot of the bed for a while, the sky streaming through my window convincing me despite guilt to linger for a little while before I, once again, confine myself in starched walls. I closed my eyes and faced the warmth, a sunflower trying to overcome withering, hoping to store energy that would last through a night of holding her hair while she retched and tried to smile through all the pain.

I must have dozed off; instead of detecting his ki like the trained youkai I was, the only sign I got of his presence was the sudden eclipse and the absence of warmth, replaced by a sudden blast of heat; for a brief moment I was reminded of Shiori's blow dryer. I knew then that when I open my eyes, I'll be faced with a look hotter than any sun, eyes flaming more than hell's furnace.

"You've been busy," he said, accusation in the tone.

"Something came up. It's no big deal," I lied, looking at him directly and unblinking.

"We can't afford distractions right now, fox."

I sighed and realized that to keep him cool, I needed to dance with his flames.

"Come, let's go to your tree," I smiled, holding his scarf and drawing him closer for a quick kiss.

"Why?" He was unfooled. But I ploughed on.

"I miss you. Stay with me while I do homework?"

"Hn," he said, eyeing me indiscreetly. But he jumped out the window and met me downstairs, and we walked side by side in a slightly more comfortable silence.

* * *

"_Come down!" the school boy said, smiling as he threw a stone up at a demon resting atop a tree._

_After a blink he was in front of him, dark apparition malignant enough to give a lifetime of nightmares, eyeing the redhead in disgust that the child knew well enough to interpret as affection._

"_How many times have I told you, ningen, to stop pecking me with pebbles!"_

_There was soft, insolent giggling as a response. "I have great news," the child said, nearing the tree and sitting cross-legged at the root of it. The apparition followed his lead, despite himself, and sat at the other side of the thick trunk._

"_Well?" he said, impatient._

"_Well…" the boy lingered, deliberately teasing. "I've found a way."_

"_I'm listening."_

"_Remember the legend of the three Reikai treasures?"_

"_Ghostslayer, Mirror of Utter Dark, and Ruffian's Sphere. Useless artifacts that give Reikai an illusion of power," the demon snorted, clearly unimpressed._

"_Perfect," the boy exclaimed. "Great you know them, will come in handy when we steal them."_

_

* * *

_

"Why do I get the feeling you're keeping something from me?"

I didn't look up, scared that my jellied resolve would make me fail in facing his question's little truth. The nights… they take more from me than what I can give. I was a candle besieged in a storm, flickering and trying his best. But the days are not enough. _I_ am not enough.

"How awful of you to assume things about me after we've spent sleepless nights perfecting this plan," I said instead, betraying honesty quite expertly and continuing to browse through a book as I sat below his tree. Our tree.

"I'm not assuming. I'm asking you."

I sighed again, knowing that this will never end until I gave him an answer. But wasn't assurance all he needed? At this point, when we were so near the day, all he must care about was being sure that I was still on board. That I was still going to do this.

"All you have to do is trust me," I said with a softer voice. "I'll get us those treasures."

"Tsk. I have no doubt about that. It's what you're going to do _after _I'm worried about."

"I won't stop you," I said, absently flipping another page. I looked up at the sun; good, it hasn't set yet, I still had time before my shift at the hospital. "You may do anything you please with your sword. But all I ask is you won't stop me or what I do with the mirror either."

I paused and tensed; that last statement gave away more than it should.

It was then that I felt Hiei's jagan opening, trying to understand the meaning behind my lies.

I leapt up to the branch he was sitting on, balanced to sit with legs dangling on either side so I was directly in front of him and his glowing forehead. I hated to do this, but it was the only way to stop him.

I put my hands up in front of Hiei, showing him the ink stains of my palm.

"Please don't," I said with a sad smile.

* * *

"_You need to tell me your weaknesses so I can protect you from them."_

"_This is not the time," he growled, looking back at the teen annoyedly. They were at a clearing in the forest park, gathered around a Reikai map, learning each and every nook and mastering navigating even with their eyes closed. The small demon was a little peeved- this was pointless exercise, he insisted quite audibly, as most of the passages they were memorizing weren't even part of their route on the way to steal the treasures. He was also frustrated – the teen, and mastermind of this heist, set the big day ten years from when he first broke the plan, which would then be five years from this moment._

_They were technically halfway there. But the length of preparation, a habit and a second in the thief's centuries-old lifetime, started to strain on the demon. If that wasn't bad enough, the teen insisted on digging up his weaknesses, a clear sign of distrust in the demon's own capabilities._

'_This is not the time' has been repeated over and over throughout the years. It was a clear message.' Now was not the time, and there will never be a time.'_

_

* * *

_

"Kaasan, don't worry, I'm holding you. You can let go," I whisper into her ear. We were at her hospital bed and I was holding a basin in front of her while holding her hair. She glanced at me with a look that was exhausted, thankful and apologetic all at the same time as she dipped her head and threw up the remains of what little dinner she had. This was a daily ritual we had, but somehow it never made things easier. The cancer had reached her stomach and was slowly wrecking havoc there, right after it was finished with her intestines.

A soft sigh told me she was finished. I wiped her mouth with a towel and proceeded to the bathroom to clean up the basin. When I reentered the room, she was already asleep. I settled myself at the couch that has been my bed for a while now, and curled up to hug myself.

To this day, I haven't made up my mind. I was going to continue with the plan, not knowing if in the end, I'll ever be strong enough to execute the last step. To live, love is the only thing I'd need. From Shiori and from Hiei, in that order. I hope he'd understand. Someday, that understanding can turn into forgiveness. I'd be happy with that. But for now, the decision has been made.

Funny, I could almost see what would become of us after this. We would remain partners, they'd make sure of that. Perhaps even more, given our body's needs. But he would never trust me again. And that will hurt me, most of all. There was no doubt as to how this would change us, even scarier would be how we might never recover. I could always put back together the shattered pieces in some deceitful fashion, but the cracks would always be there. And looking into his guarded eyes would always remind me of it.

But for now, for _her_… it was worth it. And this thought, this thought would be the one who would give me courage to execute the final step.

* * *

_He held the teen and made love to him gently, almost in adoration, like he was making love to a certain deity. After they finished, they lay down on the teen's bed, exhausted, the boy curled into a contented pose in preparation for sleep, while the demon lay stiff and seemingly unfinished._

_The boy had given himself fully to him. Without demanding for anything in exchange, without leaving doubts to his loyalty, without a flicker of hesitation in shedding his layers. What could he give in exchange?_

"_The jagan is powerful, seeing through the most powerful of youkai," he began in a low voice. The teen opened his eyes gingerly and looked at the demon to show he was listening. "But in the end, it's still an eye, and its biggest weakness is if its sight is blocked with something I cannot burn through. The simplest way would be any type of colored liquid."_

_He paused, suddenly regretful he had opened himself to such vulnerability._

_But he was reassured. "Thank you," the teen whispered, caressing his face. "I will forever protect you from your weakness. I swear it."_

_

* * *

_

To be continued. I'll post the second (and last) chapter in a few days, just cleaning it up. In the meantime, do leave your reviews to remind me why I do this lol


	2. Chapter 2

**Belated Happy Birthday, BlueUtopiah! *does a little dance***

**SPS-kun: **Thank you for your review! I didn't really read the manga so I'm just working off the anime/tv series, so this is pretty much my little own backstory to Kurama and Hiei. It works off my earlier fic, The Art of Losing a Fox.

**Disclaimer:** I don't own YYH

**The Fundamentals of Us Part 2**

"_Her name is Yukina."_

_The memory of his voice, when he said her name, inspired chills. Not because of fright, or sadness, or any emotion that lay in between. It was because of the way he whispered 'Yukina', like the name was a porcelain doll, and anything more than a whisper would break the only memory he had of her._

_It was hard to imagine a twin for this demon. That something so special, something so precious, would have something exactly like it. Did her eyes promise the same loyalty her brother's did? When she turned around, did she vanish wordlessly into the night, too? Was she broken into a million pieces, stitched together and made to present herself a valiant warrior, as faultless as he was?_

_It was the silent curiosity he had of her, this 'Yukina', that drove the red-haired teen to innocently swear that he would find her. Not for the demon, although nobody can ever find out, but for himself. After all, how many chances can one get of owning two of the most priceless jewels in the two worlds?_

_

* * *

_

I was late, but I knew he would wait. If we waited for ten years, after all, what was another couple of minutes?

As soon as I arrived, stepping on the puddles on the hard cement floor, he stepped out of the damp shadows and faced me. There was something different in him, something vulnerable in his eyes, something I was wise enough to capture in my memory; there was a big chance that I will never see this side of him again.

It was fear. Simple, undisguised, wide-eyed fear. Of us succeeding, or the plan failing, I didn't know; I took a brave guess and stabbed at the latter. Despite myself, and the knowledge that after today he would hate me for this, I rushed forward and pulled him close.

"This will work," I whispered. "I'm sure of it."

He stood stiff enveloped in my arms, and I felt his heart beating fast, pumping blood and adrenaline to feed the essential need to finally, finally take this step. Ready, finally, and yet… he smelt of trepidation. I buried my face in his hair and absorbed it, inhaling the musk of fear and chestnuts and braveness and insolence, willing it away, as if sucking and consuming it all would make everything suddenly _better_.

I couldn't blame him. The way I lay it out the plan for him was so simple, so _pure _it left no room for error. Perhaps this was what inspired this terror: steal the treasures, bargain them with Reikai for information on Yukina, find her. If any of the steps failed, there was no way to move on to the next. But he knew we had a good chance, our partnership to this was key: if there was anyone foolish enough to successfully steal from Reikai it would be me, I knew how to waggle my tongue to get what we wanted from them, he had the drive to find her wherever they pointed us, and he had the speed to evade us capture.

He didn't need to know that in my head, that plan had changed. And there was no turning back.

I've done the first step months ago.

Yusuke Urameshi, passionate high school boy. I had my eye on him for months, stalking him like a lithe deer until I knew him so well, it was frightening. But understanding him gave me confidence. His determination was unflailing, his principles honored, albeit sometimes executed in the most awkward of ways. But his passion with life assured me of my choice; that he would do it when needed, and that he take no offense.

Most of all, one day, take me in, and comfort me when Hiei's inability to absolve me would hurt the most.

And so Yusuke Urameshi was hit by a car trying to save a child's life. As expected, it was never investigated why the child was in the middle of the road, conveniently located on a street where only Yusuke was close enough to save him, or even more importantly, why the driver suddenly found himself losing control of the car. Reikai was just glad enough to swoop down on the chance to form their precious Reikai Tantei, bargaining the lad's life with the Spirit Detective job. And Yusuke would take it; I had no doubt about that.

It wouldn't be far enough after discovering their precious treasures stolen that they would send him after me and Hiei. He would do as I planned, he would lend me his life, and he would take Hiei… it was just one of the unfortunate side effects that Hiei would be unable to do anything about it.

Holding the small demon in my arms right now, I trembled. I was sure it would hurt, the pain already starting now. I tried my best to think of any other way, I was a fox sniffing through all possible roads and alleyways, but it would always lead me to this… the only way he would let me take the chance. It was an insane and elaborately complicated plan anyway, but it _had _to work. Even if it meant breaking all the promises I made, letting go of the two biggest treasures that were almost in my hands, and living a life serving the spiteful church that was Reikai, for Shiori's love… it just _had_ to.

Slowly, I let him go, knowing that I had just marked the decision to take the final step to this convoluted dance.

"Ready?" I whispered.

* * *

_One strange afternoon, resting above his tree, the demon had a thought that frightened him to his core._

_It started innocently enough; he was prepared for a completely lethargic day, glad the afternoon sun angered everyone in the planet except him. Thank god for his mixed origins; it was the one thing he could gloat over the treacherous ice maidens._

_That was what triggered the thought of his sister and how, strangely, this was the first time he thought of her for months._

_He adjusted his body as he pondered on this for a while, and to help him, he decided to picture her in his mind; the only place where she ran freely, playing in the wind and the snow in a peaceful storm, laughing like a song. He pictured her like his mother and all the ice maidens in their village, and he wondered if her eyes were red, too. In his mind she was still a child, innocent and crystal-like in her frailness. He didn't know anymore if he'd just made this actual memory up, but nobody can take away this image he had of her. Nobody. _

_Except that… except that this time, instead of snowflakes raining down at her gentle kimono, it was rose petals._

_And this thought, that the owner of the rose petals have managed to enter his mind and invade a sacred memory, rocked the very essence of his being._

_Since when had he opened himself so fully? The teen's thoughts had wound innocently around his own through the years, it was hard to determine where his ended and where the demon's started. His awareness was like ivy, slowly creeping through the walls, childlike and playful in the way it wound around all the corners and sides, caressing him and flirting with him like a siren to a sailor._

_Whose idea was it to look for Yukina?_

_The fact that he couldn't determine didn't bother him as much as the thought that with a single breath of energy from the fox, ivy can easy crumble down the biggest of mountains._

_

* * *

_

I held the hilt of the sword in my arms, holding it in an awkward way; I was no master of the weapon, as any observer would note. But I need not master the art, a sword was simple and its one end had a singular purpose. It wouldn't take an idiot to do what he pleased with it.

I knew I was taking too much time, the precious seconds ticked like a vulture circling overhead. But I had the three treasures in my arms, and all that was left was to escape; I was sure Hiei had done his part, waiting outside this corridor, silencing the whole place with invisible wards. It should be a breeze.

A breeze, of course, in the whole whirlwind of thoughts and emotions rushing through me as I slowly made my way back to him.

Somewhere far away, where everything was well and fine, and the women in our lives did not exist to complicate things for us, I knew that this would be celebrated as the one of the best heists in demon history. Hiei and I would be heroes, unseen lords in our world, cheered for in bars and pubs and passed on as legends to any demon son who would go to sleep. In there, I was youko, needing no love from the sirens, gloatingly happy over the concealed fact that aside from enjoying a venomous reputation, I owned the biggest treasure in the three worlds: the trust, loyalty, perhaps the love, of the forbidden one.

The irony made me laugh out loud: in a way, I had that in this world too.

If it weren't for human weakness, I spat inwardly, I'd have it until it did not want to be owned. Until it broke _free_. And supposedly, along with its twin.

But it would be a matter of seconds before I'd lose it all.

The darkness surrounding the castle corridor comforted me in two ways: one was that I always worked best in the darkness, the shadows concealing stealth, my power my eyes and ears. Second was unique to this moment: it hid me from my own guilt. I felt like dissolving into it, melting along with the nothingness, because isn't that what I was, at the end of it all? Ashes to ashes, those that owe their life from the earth will eventually give itself back to it, fueling life's cycles. At this point, what was I but a treacherous creature about to strike the only thing that keeps it alive? In reality I could turn my back away to this defection as easy as _her_ breathing life into me, but then, the cycle would not be complete, wouldn't it?

I double checked everything mentally, hurriedly, like a real mastermind should: Yusuke Urameshi is now spirit detective. The mirror of utter dark will heal Shiori. Yusuke would share his life with me in exchange. There was a chance we could both live.

And if we did, I needed a chance to be _free_ from Reikai prison. Thus, the most important aspect of this plot: the decoy. Make them think _he_ was the mastermind.

Ghostslayer's control over the mind of its victims was absolute. As I held the sword, its power assured me that indeed, its curse was strong enough to command even B-class demons. Strong enough to contain the flames. Oh, Hiei would be aware, for sure. But all he'll be able to do is watch, look at the damage his body is making, stare blankly at my treacherous eyes, shake with anger as his body battles Yusuke Urameshi and ultimately be led into his own defeat.

I need not be reminded that when I release it, the trapped flames would have brewed enough energy to consume me, whole.

The light breaching through the door told me that I've reached the end of my hiding. It was time. No turning back. I took a deep breath to steady myself, and turned the knob.

He had a smirk on his face as soon as I emerged with the three treasures, the sword especially held in my hand. As I walked up to him, right before I plunged the sword into his chest, I knew that the only way to pay for my sin was to let him take revenge and one day, plough the sword into my own heart.

* * *

**Notes**

Just to clarify everything, here are the five betrayals of this arc:

1. Kurama showing the ink stains of his palm was a threat to Hiei, knowing the jagan's weakness. This was a clear violation of his earlier promise to protect Hiei.

2. Kurama was the one who planted the idea of finding Yukina in Hiei's head. The sneaky thief wanted to own both treasures.

3. Just as he planted it, the fox also came up with the solution of the heist of the three treasures to bargain with Reikai information. But in the end, he had to change the plan to suit himself and save Shiori. This meant that finding Yukina was deprioritized.

4. The ending to this. Kurama plunging Ghostslayer into Hiei.

5. We all know what will happen next: Kurama takes being a traitor to a whole new level and actually smears his blood on Hiei's jagan in the warehouse fight.

**Questions that must be in everyone's minds:**

If Kurama had just told Hiei the truth, that his mother was sick and he needed the mirror of utter dark to save her life, wouldn't Hiei have shared his life too? What did he need Yusuke for?

_The mirror of utter dark wouldn't accept Hiei as much as it had Yusuke. It was the purity of Yusuke's intentions, and the willingness of Kurama to sacrifice, that would save Shiori and make the mirror grant them both their lives._

Why did Kurama need to Ghostslay Hiei?

_Kurama needed Hiei to act like a homicidal freak so when they get captured, Reikai would think Hiei was the mastermind. At this point, remember that Reikai did not know that Kurama was youko. It was a risk they'd discover if they investigated Kurama too closely. Kurama was confident enough in his negotiating abilities; he would save him and Hiei's ass from eternal damnation if they helped Yusuke and served as tantei._

_Also, Kurama thought that Hiei would not have agreed to use the mirror to save shiori. Ironically, I think he would have. But Kurama just didn't understand yet how attached Hiei had been to him at this point._

Why was Hiei dumb enough to not know Kurama's plottings

_Because he's still a busy demon; he had other things to do other than read Kurama's mind._

_Okay that was a lame excuse. But I honestly feel that he was introverted enough to not prod Kurama, even if he felt something was wrong._

Thanks for reading! This is totally new for me, I usually like creating my own worlds instead of logical plausibility, so let me know what you think.


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